Follistatin-like 1 (FSTL1) was identified as a potent cardiogenic factor secreted by epicardial cells, and application of human FSTL1 via an epicardial patch in mouse and swine models of MI stimulated cardiomyocyte proliferation, leading to an improvement in cardiac function and survival (Wei et al., 2015). Here, FSTL1 is linked to myocardial infarction.